super()

Invoke the superclass constructor by using super. In a constructor, super must appear before anything else (although in this example there isn't anything else.) Recall that even if you don't put it in explicitly the compiler will automatically put a call to super as the first thing a constructor does.

class YouthBirthday  extends  Birthday

{
  public  YouthBirthday ( String r, int years )
  {
    super ( r, years )
  }

  public void greeting()
  {
    super.greeting();
    System.out.println("How you have grown!!\n");
  }
}

When the greeting() method of a YouthBirthday object is invoked, first its superclass's method will run, then the rest of the new method will run.